Routine surveillance in southern Ohio has detected a steep increase in gonorrhea showing resistance to ciprofloxacin or reduced susceptibility to azithromycin, according to a presentation at IDWeek last week in New Orleans. Azithromycin is one of the 2 drugs in the sole recommended gonorrhea treatment regimen in the U.S., but no resistance to ceftriaxone, the other drug in that regimen, was seen.

Drug-resistant gonorrhea is a growing problem in the U.S. and worldwide. At the STD Prevention Conference in September, public health officials in Hawaii reported the first cluster of gonorrhea cases with reduced susceptibility to both azithromycin and ceftriaxone.

Thomas Herchline from Wright State University presented data from the Dayton and Montgomery County public health department STD clinic, which receives approximately 10,000 visits per year.

All clinic clients are tested for gonorrhea, chlamydia, and syphilis, and the first 10 gonococcal specimens collected each month are tested for drug susceptibility. The department participates in the CDC's Gonococcal Isolate Surveillance Project (GISP), which does resistance testing on gonorrhea specimens from STD clinics in around 30 cities.

The Ohio clinic tested 981 gonorrhea samples obtained since 1996, including 51 collected between January and July 2016. Between 1996 and 2008 they tested for resistance to ciprofloxacin, tetracycline, and azithromycin; from 2011 onward they stopped testing for tetracycline resistance and added ceftriaxone. Resistance to ciprofloxacin was defined as a minimum inhibitory concentration (MIC) of >1 µg/mL or less, while cutoffs for decreased ceftriaxone and azithromycin susceptibility were > 0.125 µg/mL and > 2 µg/mL, respectively.

Results

15.7% of tested gonorrhea isolates showed resistance to ciprofloxacin in 2016, up from none in 1996 and 2000, 1.7% in 2006-2008, 0.8% in 2011-2014, and none in 2015.

5.9% of isolates showed reduced susceptibility to azithromycin in 2016, up from none from 1996 through 2014 and 1.9% in 2015.

There was no observed decrease in susceptibility to ceftriaxone, with minimum inhibitory concentrations being variable but generally stable over time.

Regarding clinical management, Herchline said the CDC's recommended regimen of a single injection of ceftriaxone plus a single oral dose of azithromycin will still be effective for most patients with uncomplicated gonorrhea.

Due to the emergence of resistance starting in the 1990s, the CDC no longer recommends ciprofloxacin as a standard treatment for gonorrhea. It is seldom used to treat gonorrhea in at the Ohio clinic, though it is sometimes prescribed for people with allergies to the recommended drugs.

"We try to determine if there's significant risk to giving ceftriaxone," Herchline said. "Most patient, when you drill down, really it's safe to give them ceftriaxone. So we've not used [ciprofloxacin] much and now we're looking at other alternatives."